This invention relates to an insulin delivery device which permits regulation of the permeability of a negatively charged, porous membrane to stored insulin, according to the concentration of glucose in circulating body fluids. More specifically, the glucose is oxidized by the enzyme glucose oxidase to gluconic acid, which causes an alteration in the net ionic charge of the membrane, hence varying the permeability of insulin through the membrane pores. In this manner, continuous insulin release may be modified instantaneously in order to deliver appropriate doses to diabetics. The device may be used either intracorporeally or extracorporeally.
Diabetes mellitus is a disease characterized by the absence of or inappropriate secretion of insulin by the pancreas, resulting in high concentrations of glucose circulating in the blood. Periodic injection of slowly released insulin is a common treatment for this disorder, and results in a salutory decrease in the blood glucose levels. However, since the tissue demands for insulin change continuously throughout the day, such periodic administration of insulin is unable to precisely and instantaneously maintain normal glucose blood levels. In fact, administration of insulin at a continuous, uniform rate of release often has limited effect in preventing the long-term complications of diabetic hyperglycemia, namely vascular degeneration. This could lead to premature retinopathy, glomerulosclerosis, atherosclerosis, neuropathy, trophic ulceration cataract formation, glycosylation of proteins, complications of pregnancy, etc. Furthermore, simple administration of insulin is often suboptimal therapy for control of hyperglycemia in "brittle diabetics". Hence, many attempts have been made to produce devices for continuously providing appropriate amounts of insulin.